Process for recording and reproducing



May .22, 1934.. THURM 1,960,094

PROCESS FOR RECORDING AND REPRODUCING Filed Nv. 14, 1931 Hal ATTORNEY Patented May 22, 1934 UNITED STATES PATENT OFFICE PROCESS FOR RECORDING AND BEPBODUCING 15 Claims.

It has hitherto been possible to record sound waves magnetically on metallic or metalized wires or ribbons, which move in the same direction from thecommencement to the end.

The purpose of the present invention is however to superimpose a number of sound or optical records on a magnetic spiral or bobbin which can be unwound either in one direction or the other. By these means a record of much greater duration is obtained and the mechanism is simplified and several superimposed records can be transmitted simultaneously from a broadcasting station to receiving stations.

, These results are attained by appropriate changes in the speed of motion of the metal wire or ribbon, both in the recordingapparatus and in the reproducing apparatus and also by using suitable filter circuits.

In the appended drawing which is given as an example:

Fig. 1 is a diagram of the device for the magnetic registration of impulses on a metal wire or ribbon.

Fig. 2 is a diagram of the reproducing apparatus.

Fig. 3 is a diagram showing how the time required for the transmission of the recorded matter is diminished.

In Fig. 1, 1 designates a metal or metalized wire or ribbon, on which the magnetic impressions are to be recorded, said wire or ribbon being adapted to be wound on or unwound from bobbins or spools in any direction.

2 is the recording electromagnet.

3 is a filter which is intended to suppress all the frequencies not coming within certain predetermined limits, say for instance between 800 and 1200.

4 designates an amplifier in circuit with the microphone 5. i

In Fig. 2, 6 designates an earphone or a loud speaker which may bepreceded by an amplifier.

Now let it be assumed, that a steel ribbon is unrolled at a speed V whilst sounds are recorded thereon by means of a microphone with or without an amplifier in the circuit before the inscribing or recording electromagnet, an electric filter being interpolated which will only allow frequencies between 800 and 1200 to pass for instance (Fig. 1) i If, after the recording is effected, the microphone and its amplifier is replaced by an earphone or loud speaker preceded by an amplifier, then as the ribbon or wire is unwound in the same direction and at the same speed V (Fig. 2) the sounds previously recorded by the microphone will be heard. On the other hand, if the spiral is caused-to be unwound at twice the speed, i. e. 2V between the poles of the reproducing electromagnet (Fig. 2) then the previously recorded frequencies between 800 and 1200 affect the receiving electromagnet as if they were frequencies between 1600 and 2400 the latter may be considered their eifective frequency band under the 2V unwinding speed conditions. As the filter only passes frequencies between 800 and 1200, the earphone or loud speaker remains silent. The metal spiral will therefore, as regards the receiving device, behave as if no record had been impressed on it.

It will therefore be possible to impress a record on it with the device of Fig. 1, while the strip moves at a speed equal to 2V and to listen to the second record with the device of Fig. 2, whilst the strip moves at the speed 2V.

If the spiral is caused to be unwound at a speed 3V when neither the first nor the second record will be audible with the device of Fig. 2, because the first record is transposed (as regards the reproducing electromagnet) in effective frequency into the band comprised between 2400 and 3600, and the second record is transposed in effective frequency into the band between the frequencies of 1200 and 1800. It will thus be possible to make a third record by means of the device shown in Fig. 1, the ribbon travelling at a speed 3V. It is obvious that the three effective frequency bands at the 3V speed of unwinding, i. e., 800-1200, 1200-1800, and 2400-3600 are discrete, that is to say non-overlapping, as a result of speed ratios at least as great as the ratio between the upper and lower limits of the band passed by the filter, i. e., 1200:800.

It is further obvious that while the effective fre- 9d quency bands vary with the speed of unwinding, they remain discrete and of mutual identical logarithmic width, i. e., ratio of upper to lower limit.

It is therefore possible to listen at will to the first, second or third record, according to whether the ribbon travels at a speed equal to V, 2V or 3V. With four speeds, four superimposed records are possible and'so on. This process for superimposing records one on another (in the case of the wireless transmission or transmission by wire between the sending and receiving stations) also presents the following advantage, viz:

for n superimposed records thus effected, the 11 0 length of the record transmitted can be multiplied by if the ribbon is during the transmission unwound at a speed of n.V.

It is thus for instance possible to transmit a message which is, telephoned and recorded on a spiral in 4 superimposed records, from Europe to America in At the end of each of these 4 minutes the reg- I istering electromagnet will successively arrive at c, d, e, B as shown by the arrows. The second recording which is effected at a speed of V" may last for say 3 minutes, and at the end of the fifth, sixth, and seventh minute the recording electromagnet has arrived at f. y The third superimposed message which is effected at a speed V' lasts for 2 minutes, and the recording electromagnet arrives respectively at d and B at the end of the eighth and ninth minute of registering. The fourth record is made at a speed V"" and lasts one minute,-i. e. the tenth during which the receiving electromagnet moves from B to A.

During the eleventh minute the whole of the recorded message which has taken 10 minutes to record, can be transmitted (consequently in I 10 times less time) from the sending to the reeeiving station, which latter analyses after reception the complete message by means of the device above described.

It is of course understood that this process is absolutely independent of any mechanical or electrical device which may be used to carry it into practice.

. -I claim:

1. A process of the character described comprising impressing electro-magnetically a number of separate records in superimposed relation upon a recording element, and imparting a different movement to the recording element for each record being impressed thereon.

. 2. A process of the character described comprising impressing electro-magnetically separate records in superimposed relation upon a recording element, and displacing the recording element in a different direction and at a, different speed'for each record impressed thereon.

3. A process of the character described comprising impressing electro-magnetically separate records in superimposed relation upon a recording element, displacing the recording element in a different direction and'at a different speed for each record impressed thereon whereby to vary the frequency band of each of said impressed records and suppressing all frequencies subject to deleteriously affect the subsequent reading of the superimposed records. I v

4. A process of the character described comprising impressing electro -magnetically separate records in superimposed relation upon a recording element, imparting a different movement to the recording element for each record being impressed thereon whereby to vary the frequency band of each of said impressed records, and conducting the electro-magnetic impressions through filters to supress all frequencies subject to deleteriously affect the subsequent reading of the superimposed records.

5. A process of the character described comprising impressing electro-magnetically separate records in superimposed relation upon a recording element, imparting a different movement to the recording elementfor each record impressed thereon whereby to vary the frequency band of each of said records, and translating the records in a reproducing circuit for the separate reproduction of the successive superimposed records.

6. A process of the character described comprising impressing electro-magnetically separate records in superimposed relation upon a recording element, imparting a different movement to the recording element for each record impressed thereon whereby to vary the frequency band of each of said records, and translating the records in a reproducing circuit for the successive reproductions of the different superimposed records by changing the speeds of travel of the recording element.

7. In the recordation of impulses upon and the reduction thereof from a single moving record, the method of superimposing and analytically reproducing a plurality of successive recordings, which includes imparting to said record during each of said recordings a respectively different velocity, and successively imparting to said record duringsaid reproduction therefrom velocities respectively corresponding to said first mentioned velocities.

8. In reproduction from a single moving record upon which has been superimposed a plurality of recordings having at any given record velocity discrete effective frequency bands of substantially a single logarithmic width, the method of selectively reproducing said recordings which comprises restricting the band of frequencies subject to said reproduction to a fixed band having substantially said logarithmic width, and selectively establishing the velocity of said record to make substantially coincident with said fixed band any desired one of said discrete frequency bands.

9. In the recordation of multi-frequency impulses upon a single moving record, the method of superimposing a plurality of successive recordings while maintaining the same reproducibly distinct, which includes restricting the frequency band of said impulses to predetermined limits,

and imparting to said record during the respective said recordings respectively different velocities.

10. In the recordation of multi-frequency impulses upon a single moving record, the method of superimposing a plurality of successive recordings while maintaining the same reproducibly distinct, which includes restricting the frequency' band of said impulses to predetermined limits; and imparting to said record during the respective said recordings velocities progressively related each to the preceding in at least the ratio between the limits of said band.

11. In the recordation of multi-frequency impulses upon and the reproduction thereof from a single moving record, the method of superimposing and analytically reproducing a plurality of successive recordings, which includes restricting the frequency band of said impulses to predetermined limits, imparting to said record during the respective said recordings respectively different velocities, restricting the frequency band subject to said reproduction substantially to said predetermined limits, and successively imparting to said record during said reproduction velocities respectively similar to said first mentioned velocities.

12. In the recordation of multi-frequency impulses upon and the reproduction thereof from a single moving record, the method of superimposing and analytically reproducing a plurality of successive recordings, which includes restricting the frequency band of said impulses to predetermined limits, imparting to said record during the respective said recordings velocities progressively related each to the preceding in at least the ratio between the limits of said band, restricting the frequency band subject to said reproduction substantially to said predetermined limits, and successively imparting to said record during said reproduction velocities respectively similar to said first mentioned velocities.

13. In the recordation of multi-frequency' impulses upon and the reproduction thereof from a single moving record, the method of superimposing and selectively reproducing a plurality of successive recordings, which comprises restricting the frequency band of said impulses to predetermined limits, imparting difierent velocities to said record during the respective said recordings whereby to produce in said record a superimposition of recordings having at any given recdiscrete in said recording the eilfective Irequency bands of said respective trains by progressively varying the speeds oi! eflecting the respective said recordings, and transmitting said recordings in said superimposed relationship.

15. In the electrical transmission oi successive multi-frequency impulses, the method of reducing the time required for such transmission, which includes restricting to predetermined limits the absolute frequency band of all of said impulses, successively recording successive trains of said impulses in superimposed relationship, maintaining discrete in said recording the eiIective frequency bands of said respective trains by progressively varying the speeds of eirecting the respective saidrecordings, and transmitting said recordings in said superimposed relationship.

LEON THURM. 

